1. Field of the Invention
The present invention relates to a phase comparator arrangement for controlling an electrical member by altering its supply in accordance with the phase difference found between two square wave and/or pulsed waveforms, and more particularly to an arrangement of this kind in which one of the waveforms represents a measurement of operating characteristics of the electrical member being controlled, and hence an arrangement which operates in a system which is looped back to an input of the phase comparator with which the system commences.
2. Description of the Prior Art
There are known phase comparator circuits, called relative phase detectors, which emit pulses whose length is modulated in proportion to the phase difference measured between two periodic square waves. Certain of these circuits make such measurements over a range of .+-.180.degree.. Generally speaking, relative phase detectors of this kind employ one or two bistable flip-flops and have two outputs, one of which is assigned to advances in relative phase and the other to lags. Such a phase difference detector is described in French patent application No. 74 12745, the introduction to which also reviews structures antedating that which the patent proposes.
This patent provides a brief description of the system in which its phase difference detector is intended to operate, which system is shown in outline in the block diagram in accompanying FIG. 1. Referring to FIG. 1, an oscillator OSC is follwed by a frequency divider 1/N which emits a periodic square waveform HOR. A phase comparator circuit CP receives this waveform HOR, which is termed the "measurement" waveform, and compares its phase with that of another waveform INF which is termed the "reference" waveform. The pulses (the signals for the phase difference measured) from comparator CP are applied to a control circuit CC for controlling the frequency and phase of the oscillator OSC.
However, this arrangement, like those described in the preamble to the French patent, is only practicable in arrangements wherein the "reference" waveform, like the "measurement" waveform, is a square wave and periodic. In each of these two waveforms, there is a specific, constant cyclic ratio and their mean frequencies are close to the ordered frequency of the oscillator to be controlled. Such arrangements are clearly unsuitable for dealing with non-periodic control input waveforms in which the cyclic ratio varies.